Like dimly-lit alleyways and late-night subway platforms, Walmart parking lots can be unsafe spots. During the Black Friday shopping rush last year, two people were shot outside a Florida Walmart. Last month, there were shootings outside two other Walmarts in the same state. And another gun came out in the parking lot of a Florida Walmart on Friday, after an employee refused to accept a woman's "dollar-off" coupon.

Mary Frances Alday, 61, tried to redeem an Internet coupon at the Walmart in Crawfordville, according to a Wakulla County Sheriff's Office filing, and reported by The Smoking Gun. The accounts say that when assistant manager Tracy Stockslager explained that Walmart didn't accept that kind of coupon, it sent Alday into a fury.

Stockslager told police that Alday "called her a bitch and other foul names and intentionally hit her with a shopping cart." Stockslager claims that she then escorted Alday to the door while calling 911. Alday reportedly cautioned Stockslager not to follow her outside, to which Stockslager replied that she was going to note the license plate number on Alday's car.

According to the police report, Alday said, "If you follow me, I have something in my car for you." Alday then went to her car, pulled a handgun out from the passenger's seat and waved it around in its holster. She then removed it from the case, and pointed it at Stockslager and other Walmart employees who had joined her just outside the store. Alday then said, "I have something for y'all." Stockslager and the other employees raced back inside the Walmart, the report says, "in fear of their lives."

A deputy sheriff caught up with Alday soon after, police say, and used a stun gun on the disgruntled Walmart shopper because she refused to leave her car. Alday has been charged with four counts of aggravated assault with a deadly weapon and one count of battery.

It might not be surprising that Walmart has been the scene of such incidents since the retailer gets more than 200 million visits to its stores each week. But their frequency has raised some concerns. When a woman, who had been abducted from a Walmart parking lot and then raped, sued the retail chain, the Supreme Court of Appeals of West Virginia said, in granting her a new trial, "A quick search of reported cases reveals that Wal-Mart parking lots are a virtual magnet for crime."

But Walmart has a robust security operation, including "asset protection" staff, who are "responsible for all levels of security strategy," according to the retailer's website, as well as armed security guards at certain locations. Some of those guards have themselves been implicated in violent incidents at the retail chain, though. Last December, an off-duty police officer working security at a Texas Walmart allegedly shot and killed a suspected shoplifter trying to flee, and since 2005 at least three other alleged shoplifters have died after struggles with asset protection staff, according to various news reports.